Various aluminate phosphors have been put to practical use as phosphors for energy-saving fluorescent lamps. As a blue phosphor, for example, (Ba,Sr)MgAl10O17:Eu is mentioned. As a green phosphor, for example, CeMgAl10O19:Tb, BaMgAl10O17:Eu,Mn, and the like are mentioned.
In recent years, (Ba,Sr)MgAl10O17:Eu, which has high luminance under vacuum-ultraviolet excitation, has been used as a blue phosphor for a plasma display panel.
However, when a PDP, especially one using the blue phosphor (Ba,Sr)MgAl10O17:Eu, is driven for a long period, the luminance is degraded significantly. Hence, in the PDP use, there is a strong demand for a phosphor that shows less luminance degradation even after the long-time driving.
In response to this demand, a method using a silicate phosphor has been proposed (see, for example, JP 2003-132803 A).
However, the above-mentioned conventional method has not achieved inhibition of the luminance degradation of the phosphor during PDP driving, while maintaining the high luminance. Moreover, the chromaticity y is higher and the color purity is worse than those of a blue phosphor (Ba,Sr)MgAl10O17:Eu (BAM:Eu) that currently is used in the PDP.